Epstein-Barr virus (EBV) is a human tumor virus discovered in Burkitt's lymphoma (BL) and subsequently linked to multiple cancers. In vitro, EBV infection confers on B lymphocytes an unlimited growth potential termed immortalization. The long-term goal of this research is to understand the mechanisms by which EBV causes cancer. Toward this end, our laboratory has developed a novel cell system in which EBV episomes can be eradicated from Burkitt's lymphoma cells by treatment with low-dose hydroxyurea. Burkitt cells "cured" of EBV lose their malignant growth phenotype despite retaining the hallmark t(8;14) in which c-myc is translocated into an immunoglobulin locus. Using gene arrays to compare global gene expression patterns in paired EBV-positive and EBV-negative BL clones, a 3-fold reduction in spermidine/spermine N1-acetyltransferase (SSAT) in EBV-positive (malignant) cells was among the very limited changes that distinguished these closely related clones. Because the translocation and subsequent deregulation of c-myc in BL result in overexpression of ornithine decarboxylase (an enzyme involved in biosynthesis of polyamines essential to cell growth), the finding that EBV infection downregulates SSAT (an enzyme involved in polyamine catabolism) formed the basis for our hypothesis: EBV infection manipulates the polyamine metabolic pathway to provide a growth advantage that not only favors viral persistence but also contributes to tumorigenesis in B cells. Specific aims to test this hypothesis are: 1) Quantify differences in polyamine catabolism between EBV-positive BL cells and their EBV-negative subclones by examining transcriptional and translational controls involved in SSAT regulation and by measuring polyamine levels; 2) Identify the type 1 latency viral gene product(s) that affect(s) SSAT expression, by stable transfection techniques; 3) Determine whether forced expression of SSAT reverses the malignant phenotype in EBV-positive cells, using a conditional expression SSAT construct or treatment with a polyamine analogue that is a potent inducer of SSAT.